热封（4A区）
We are finishing off a room in the attic, above an unheated 2 car garage. The room has 5 ft knee walls and a cathedral ceiling. There are no HVAC components behind the knee wall. The floor of the room is already insulated (R30 batt) to the garage below and has OSB flooring. The room will be heated/cooled with a high seer mini-split ductless heat pump. We plan on using open-cell spray foam between the rafters in the ceiling. I believe we have 2 options. First is to spray from the ridge vent all the way to the soffits and insulate the floor behind the knee walls (that space overlies the garage as well but is currently not insulated or floored) with either spay foam or batt or cellulose. If we do that, I assume we don’t have to insulate the knee wall itself. The second option is to spray from ridge vent to just beyond the knee wall and then insulate the knee wall itself with batt that has an air block behind it (OSB). From the information I have gathered from reading this forum, I believe the advice will be to go with the first option, but I have a question. If I go with the first option, the area behind the sheetrocked knee wall, even though it becomes located inside the thermal envelope, is not heated or cooled, and will always be either hotter or cooler than the finished room. Won’t that negatively effect the temp inside the finished room and cause the heat pump to work harder than if I insulated the knee wall itself?
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Replies
抢劫
1. You need to make sure the wall to the house and floor system under the bonus room is closed and sealed from the rest of the house.
2.您有3个选项来封装阁楼：a）在屋顶装饰下安装闭孔泡沫，仅符合R38，或b）2“封闭的泡沫加开孔，以满足R38，或C）安装2”刚性泡沫上方护套（它需要更换）和屋顶护套下的开放式电池，以满足R38。
3. BATT绝缘非常渗透并在占地面积下安装错误。有一旦您有选择1的奖金室，您将在奖金室内从车库中吸入空气和烟雾。您需要拆下这些底板并安装2“封闭电池泡沫，然后可以用玻璃纤维素或玻璃纤维绝缘层填充腔，或全部关闭电池泡沫，或封闭/开放式电池泡沫。
4. If you encapsulate the whole attic, you do not need to insulate the knee wall.
2) My inspector has told me that for the angled cathedral ceiling, R30 meets code; I would really prefer not to use closed cell on the roof line
4) I just don't understand how the non-heated/cooled space behind the knee wall will not negatively effect the temp in the finished room
- 402.2.2 Ceilings without attic spaces. Where Section 402.1.1 would require insulation levels above R-30 and the design of the roof/ceiling assembly does not allow sufficient space for the required insulation, the minimum required insulation for such roof/ceiling assemblies shall be R-30. This reduction of insulation from the requirements of Section 402.1.1 shall be limited to 500 square feet or 20 percent of the total insulated ceiling area [for the whole house, not just one room], whichever is less.
- Some open cell foams are air impermeable at 5.5", some at 7, and some at 10". As long as you have room to have the right amount you could be ok... See 2009 IRC R806.4, and N1102.2.2 or 2009 IECC 402.2.2 (above)
抢劫
如果您沿着倾斜屋顶安装绝缘，请将绝缘延伸到屋檐，然后膝盖墙后面的区域将在房屋的条件包围内。假设您对空气密封和绝缘的良好工作，膝盖墙后面的温度将接近您房屋的条件区域的温度。信不信由你。